Penkayak, welcome to the forum.I haven't seen a broken crank arm in a few years -- it seems to be uncommon around here.

There appears to be quite a bit of corrosion around the lower broken crank arm hole. Does your drum have a weep hole in the bottom. If not, it might be a good idea to drill a small one so salt water can not sit in that pocket. Even if you rinse and drain it, there is a residual in the hollow pedal arm shaft that drains back into that area.

Years ago Hobie used solid billet aluminum crank arms. They are still listed in the catalog (81105001 crank arm right, threaded; and 81100001 crank arm left threaded) -- they are very strong and you'll never break them, but they require standard bicycle screw-on pedals (left and right hand threads) which you'll have to supply. They should be otherwise interchangeable with the current crank arms.

Penkayak, welcome to the forum.I haven't seen a broken crank arm in a few years -- it seems to be uncommon around here.

There appears to be quite a bit of corrosion around the lower broken crank arm hole. Does your drum have a weep hole in the bottom. If not, it might be a good idea to drill a small one so salt water can not sit in that pocket. Even if you rinse and drain it, there is a residual in the hollow pedal arm shaft that drains back into that area.

Years ago Hobie used solid billet aluminum crank arms. They are still listed in the catalog (81105001 crank arm right, threaded; and 81100001 crank arm left threaded) -- they are very strong and you'll never break them, but they require standard bicycle screw-on pedals (left and right hand threads) which you'll have to supply. They should be otherwise interchangeable with the current crank arms.

thank you advice Roadrunneror drill the hole without weakening the drum

The breakage was on a second hand drive I bought. I do not think that the drive had been particularly well cared-for: there was certainly more corrosion on either of my other drives and I seem to remember that the blanking plug on the top of the arm (to stop water coming in the end) was missing.

It started twisting noticeably before it finally broke in the middle across the adjustment holes like one of your photos.

I think the answer is that the arms do wear and break, especially if not cared for properly and used hard (I would not class myself as a particularly light user) so keep the plugs in place, rinse well after use in salt water and consider stocking a spare. The good thing is that spares are available and replacement is straightforward.

Years ago Hobie used solid billet aluminum crank arms. They are still listed in the catalog (81105001 crank arm right, threaded; and 81100001 crank arm left threaded) -- they are very strong and you'll never break them, but they require standard bicycle screw-on pedals (left and right hand threads) which you'll have to supply. They should be otherwise interchangeable with the current crank arms.

Nice! Had no idea and have been thinking about fabricating this very thing. Do they weigh more?

_________________"Never mistake a clear view for a short journey." - Cowboy Proverb

Penkayak, Your drive shows corosion. This can be prevented with a good spray lubricant applied weekly. WD40 works fine but I prefer any of the new waterproof silicones now on the market. Any automotive store should have them. I have drives over 10 years old that have zero corosion but get sprayed all the time.After four years of use however you might excpect something to give.

The crank arm corrosion is a byproduct of galvanic action where two different metals are touching in the presence of moisture. Salt water accelerates the process. In this case where you have stainless steel and aluminum, the aluminum corrodes.

The best way to protect the aluminum is by adding a third metal such as zinc. The zinc acts as a "sacrificial annode" and will corode instead of the aluminum. Fortunately zinc is inexpensive and very common. In fact, any 1983 and newer U S cent is 97.5% zinc.

Look for a worn penny where the copper cladding is mostly worn off,

bend it to fit in your pedal shaft and slide it in.

BTW, the crank arms are now anodized for better durability. They used to be E coated (painted). Between the improved crank arms and one penny fix (check it annually for replacement), you shouldn't have any further problems.

PS. I checked out the drums. They do have a drain hole:

But the hole doesn't drain completely (residual water is highlighted in pink):

So it is best to rinse turning the Drive upside down a few times to purge the salt water (which also leaks into the shaft of the crank arms).

Nice! Had no idea and have been thinking about fabricating this very thing. Do they weigh more?

Yes, they are quite a bit heavier. So are the bicycle pedals you'll be using. The original style Drives weighed significantly more than the current versions. I don't see it as especially problematic though -- they all sink!